It's quite random, really; some items can triple in price almost immediately after release while others hit the bargain bin. Personally I think it's safer to preorder, because usually they don't fall below 20-30% below preorder price, but can increase to easily double or more. Also, they release in october of this year i thought :0

Do you want to buy 6? If that's the case you're probably better off ordering them from goodsmiles shop in one order. The order itself will cost a lot but you're only going to pay 2k yen shipping for all 6, even if they arrive at different times.

This. As an almost exclusively Nendo collector, I find myself cursing my negligence in keeping up on figure news. Missing pre-orders can result in trying to get figures at double or triple their original price.

It's a gamble. The preorder price is the lowest possible price from the manufacturer, but if after release the figure ends up being overstocked/unpopular/not selling as fast as expected for resellers, then some resellers will willingly take a hit and clearance them lower than the price they bought them for. (The figma for Sword Art Online 2's Elf Asuna's been on clearance at a lot of stores from what I've seen, some going as low as 40% off preorder price.) On the other hand, if the figma is really popular on release, then the price is likely to shoot straight up and never dip into clearance (a few of the Fate figma have done this shooting up 20% then 50% then double release price and higher).

If you're planning on getting a full set of Osomatsu brothers, you should at least plan to preorder one or two, so you'll be guaranteed them at the preorder price. Then it's just a matter of if you want to gamble that for the rest they'll hit a lower clearance price after release and save you money.

It can technically go either way. Sometimes supply is too low to meet demands and figure X goes OOS/backorder with a price hike, or the price drops significantly thanks to a combination of poor sales and the inherent desire to clear inventory space.

This character you've mentioned is a mystery to me, so I can't comment on his popularity. Also I've noticed the variation/posing of the figure matters greatly. The RAH uniform Ryuko costs more than 2x that of the RAH Senkets Ryuko.

The reason the uniform Ryoko costs so much more was that she was a very limited and exclusive release, while her Senketsu version was a standard release, which in the case of RAH's often drop in price after release.

Not so sure about that varient, it's been sitting there for ages with no news. It may well have been cancelled. Then again, it may just have been delayed and could randomly go up for preorder with little warning, as with many RAH's, so all we can do is wait really.